全文获取类型
收费全文 | 195篇 |
免费 | 56篇 |
国内免费 | 61篇 |
专业分类
化学 | 112篇 |
晶体学 | 15篇 |
力学 | 34篇 |
综合类 | 4篇 |
数学 | 18篇 |
物理学 | 129篇 |
出版年
2024年 | 6篇 |
2023年 | 18篇 |
2022年 | 23篇 |
2021年 | 9篇 |
2020年 | 4篇 |
2019年 | 25篇 |
2018年 | 23篇 |
2017年 | 11篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 23篇 |
2013年 | 11篇 |
2012年 | 9篇 |
2011年 | 16篇 |
2010年 | 10篇 |
2009年 | 11篇 |
2008年 | 14篇 |
2007年 | 13篇 |
2006年 | 9篇 |
2005年 | 16篇 |
2004年 | 7篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有312条查询结果,搜索用时 15 毫秒
51.
铝合金是国内外研究堆的主要结构材料,在前期300#研究堆主要结构材料铝合金辐照性能研究的基础上,通过离子辐照研究6061-Al合金的微观结构损伤和引起的硬度变化,以开展较高辐照剂量下6061-Al合金损伤效应的前期探索。结果表明,经过自离子辐照后,6061-Al合金中产生了夹角为72°的位错环等缺陷,随着辐照剂量从0.218×1016 cm?2增加到4.367×1016 cm?2,缺陷密度明显增加,但选区电子衍射表明合金保持了很好的晶体结构,并没有发生非晶化。纳米压痕测试表明,不同辐照剂量下,样品中产生了不同程度的硬化,且微观硬度随着辐照剂量的增加而增加,当剂量增加到2.183×1016和4.367×1016 cm?2时,辐照硬化达到饱和,约为11%。研究结果可为初步预测较高中子辐照剂量下6061-Al合金结构和性能的变化提供数据支撑。 相似文献
52.
随SPRR-300研究堆约30 a的长时间运行,位于活性区附近的石墨箱体经历了长期的中子辐照。在长期服役的石墨箱体上取样,研究了其热学、力学以及微观结构变化,并与商用IG110,NG-CT-10石墨进行了对比。研究结果表明,经长时间低剂量率的中子辐照后,SPRR-300堆内随堆辐照石墨的晶格中出现了明显的辐照损伤缺陷,这些缺陷主要为位错环、层错、孔洞和微裂纹等,并出现了一定程度的非晶化。这些辐照损伤缺陷直接或间接地引起了石墨热学、力学性能的变化,主要表现为热膨胀系数、热扩散系数、抗压强度和抗弯强度的下降以及弯曲弹性模量的上升。 相似文献
53.
Development of an electronic stopping power model based on deep learning and its application in ion range prediction 下载免费PDF全文
Deep learning algorithm emerges as a new method to take the raw features from large dataset and mine their deep implicit relations, which is promising for solving traditional physical challenges. A particularly intricate and difficult challenge is the energy loss mechanism of energetic ions in solid, where accurate prediction of stopping power is a long-time problem. In this work, we develop a deep-learning-based stopping power model with high overall accuracy, and overcome the long-standing deficiency of the existing classical models by improving the predictive accuracy of stopping power for ultra-heavy ion with low energy, and the corresponding projected range. This electronic stopping power model, based on deep learning algorithm, could be hopefully applied for the study of ion-solid interaction mechanism and enormous relevant applications. 相似文献
54.
Microwave absorption properties regulation and bandwidth formula of oriented Y2Fe17N3-δ@SiO2/PU composite synthesized by reduction-diffusion method 下载免费PDF全文
As concepts closely related to microwave absorption properties, impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms. In this work, reduction-diffusion method was innovatively applied to synthesize rare earth alloy Y$_{2}$Fe$_{17}$. In order to regulate the electromagnetic parameters of absorbers, the Y$_{2}$Fe$_{17}$N$_{3-\delta }$ particles were coated with silica (Y$_{2}$Fe$_{17}$N$_{3-\delta }$@SiO$_{2}$) and absorbers with different volume fractions were prepared. The relationship between impedance matching, matching thickness, and the strongest reflection loss peak (${\rm RL}_{\rm min}$) was presented obviously. Compared to the microwave absorption properties of Y$_{2}$Fe$_{17}$N$_{3-\delta }$/PU absorber, Y$_{2}$Fe$_{17}$N$_{3-\delta }$@SiO$_{2}$/PU absorbers are more conducive to the realization of microwave absorption material standards which are thin thickness, light weight, strong absorbing intensity, and broad bandwidth. Based on microwave frequency bands, the microwave absorption properties of the absorbers were analyzed and the related parameters were listed. As an important parameter related to perfect matching, reflection factor ($\sqrt {ărepsilon_{\rm r}/\mu_{\rm r}}$) was discussed combined with microwave amplitude attenuation. According to the origin and mathematical model of bandwidth, the formula of EAB (${\rm RL}<-10$ dB) was derived and simplified. The calculated bandwidths agreed well with experimental results. 相似文献
55.
The major results of a series of our recent investigations on the adsorption of eight amino acids on Cu(001) and (111) surfaces are reviewed in the present paper. In all studied cases the molecules adsorb onto the surface in their anionic form. With the increase of the coverage three different 2D phases of the adsorbates, that is, the 2D lattice gas, intermediate, and solid phases, appear sequentially, although for few systems one or two of them do not appear. In both the 2D lattice gas and intermediate phases the molecules "stand" with their two oxygen "feet" on the surface and the intermolecular interactions are repulsive, although in the former they can diffuse frequently whereas in the latter they are discommensurate in one direction with the substrate. In the solid phase the molecules "lie" down on the surface to form commensurate superstructures. Adsorption of amino acids may often induce step faceting as well as bunching to form facets. Adsorption of L-lysine on Cu(001) may cause steps bunching to form facets with all the same chirality. Our preliminary results show that it is possible to manipulate individual molecules with the STM tip even at room temperature. These results may have applications in nano-materials, nano-technology, and very likely also in chiral separations or enantioselective heterogeneous catalysis. 相似文献
56.
57.
59.
60.